Self-contained fluid-power servomechanism

ABSTRACT

An example method of using a servomechanism can include controlling a reversible positive displacement pump that is located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that is rotably disposed in a second chamber of a housing to rotate an output shaft that is coupled to the vane and controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to reverse rotation of the output shaft.

BACKGROUND

Servomechanisms or servos are devices that can use feedback or error-correction signals to control operation of a mechanism. Servos typically include a motor (e.g., an electrical motor) that can control the angular orientation of an output shaft, which in turn can be coupled to a movable control surface or component of a mechanical system. Servos, for example, can be used in unmanned aircraft or air vehicles to precisely and dynamically position control surfaces such as elevators and rudders. They can additionally be used for steering vehicles, such as radio controlled boats, cars and trucks.

The output shaft can typically be positioned to specific angular positions in accordance with a coded signal received by the servo. It is common that a particular angular position will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the shaft can change accordingly.

Control circuits and a potentiometer are typically included within the servo motor casing and are functionally connected to the output shaft. Through the potentiometer (e.g., a variable resistor), the control circuitry is able to monitor the angle of the output shaft. If the shaft is at the correct angle, the motor actuates no further changes. If the shaft is not at the correct angle, the motor is actuated in an appropriate direction until the angle is correct. Thus servos can function on a principle of negative feedback, where a control input is compared to the actual measured position of a mechanical system. A difference between the actual and desired value (i.e., an error or “error signal”) can be used to drive the system in a direction to reduce or eliminate the error.

One concern with conventional servos is that they can have limited adjustment resolution. Conventional servos rely on a geared transmission to couple an electrical motor one or both a feedback sensor and an output shaft. While the system can demonstrate acceptable precision and accuracy when new, the gear train can quickly degrade, increasing gear lash and decreasing precision and accuracy over time. The increase in gear lash can even decrease the number of discrete adjustment positions available to the user.

Such decreases in precision can cause servomechanism controlled systems to be undesirably difficult to control. For example, hobbyists who practice dynamic soaring must control an unmanned aircraft travelling over 400 miles per hour. At such a high rate of speed, even a small decrease in precision can result in a dramatic increase in the difficulty of vehicle control. Racers operating touring cars that travel at high rates of speed similarly demand precise control. Vehicles that frequently apply high levels of intermittent stress, such as by torqueing the servomechanism, additionally benefit from an ability of the servomechanism to endure counter-torque inputs, such as when a wheel of the vehicle hits an obstacle, applying a counter torque to the servomechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIG. 1 is an elevated right perspective view of a servomechanism, according to an example.

FIG. 2A is a lower right perspective view of a servomechanism, according to an example.

FIG. 2B is a lower perspective view of the vane illustrated in FIG. 2A.

FIG. 2C is another lower perspective view of the vane of FIG. 2A.

FIG. 2D is a lower perspective view of the vane illustrated in FIG. 2A.

FIG. 3 is a fluid circuit diagram showing an over-torque bleeding circuit of a servosaver, according to an example.

FIG. 4 is a fluid circuit diagram showing an over-torque bleeding circuit of a servosaver, according to an example.

FIG. 5 is a fluid circuit diagram showing a make-up reservoir, according to an example.

FIG. 6 is a cross section side view of a servomechanism, according to an example.

FIG. 7A is a cross-section side view of a vane, according to an example.

FIG. 7B is a bottom view of the vane illustrated in FIG. 7A.

FIG. 8A is a top view of a top portion of a servomechanism housing, according to an example.

FIG. 8B is a hidden line side-view of the housing portion of FIG. 8A.

FIG. 8C is a bottom hidden line view of the housing portion of FIG. 8A.

FIG. 8D is a left-side view of FIG. 8C.

FIG. 8E is a left-side view of FIG. 8C.

FIG. 9A is a top view of a middle portion of a servomechanism housing, according to an example.

FIG. 9B is the front hidden line view of the housing of FIG. 9A.

FIG. 9C is a left side hidden line view of the housing illustrated in of FIG. 9B.

FIG. 9D is a right side hidden line view of the housing illustrated in of FIG. 9B.

FIG. 10 is a bottom view of a middle portion of a servomechanism with components disposed therein, according to an example.

FIG. 11A is a top view of a bottom housing portion, according to an example.

FIG. 11B is side view of the housing portion of FIG. 11A.

FIG. 12A is a front view of a reservoir cover, according to an example.

FIG. 12B is a cross-section right side view of the reservoir cover of FIG. 12A.

FIG. 13 is a cross-section side view of a reservoir piston, according to an example.

FIG. 14 is a flow chart showing a method of using a servomechanism, according to an example.

FIG. 15 is a flow chart showing a method of assembling a servomechanism, according to an example.

DETAILED DESCRIPTION

Servomechanism embodiments of the present subject matter address the shortcomings disclosed above by using an internal hydraulic or fluid-power pump and motor pair to translate motion from an electric motor into servo shaft motion. These embodiments can thus translate electronic input signals into rotary output motion. A major advance of the present subject matter is that it reduces or eliminates the problem of gear lash increasing over time. Embodiments have little or no lash because fluid connecting the pump to the motor is highly incompressible (i.e., it has a high bulk modulus) and thus cannot become loose over time as a gear train does. Further, embodiments can include a reservoir to make up for fluid volume changes in the system either from temperature variations or lost fluid, further ensuring that a high bulk modulus fluid coupling between the motor and the pump is maintained, providing for long-term precise control of the motor via the fluid-power link. Of course, embodiments can be bled to ensure that the fluid coupling is composed of high bulk modulus fluid like oil, as opposed to air, which has a low bulk modulus and is thus compressible.

FIG. 1 is an elevated right perspective view of a servomechanism, according to an example. The servomechanism 100 includes a housing 102. The servomechanism includes an output shaft 104. At least one end 112 of the output shaft can be splined 106. The splines 106 can mate with another component, such as a servo horn. An exterior profile 108 of the servomechanism 100 can be sized to be disposed in a space sized to receive a hobby servomechanism. One example of a hobby servomechanism is the Futaba S-148 servomechanism available from Futaba Corporation of America located in Schaumburg, Ill., although the present subject matter is not so limited. Flanges 110 can be used to secure the servomechanism in position in use, such as when it is being used to actuate a control surface of an unmanned vehicle such as a radio-controlled (“RC”) airplane such as a glider.

FIG. 2A is a lower right perspective view of a portion of servomechanism 200, according to an example. FIG. 2D is a lower perspective view of the vane illustrated in FIG. 2A. A housing top portion 202 of a housing is shown, with remaining portions not shown to better illustrate an example internal configuration. The output shaft 204 is shown at the top of the servomechanism 200. Flanges 206 are also shown and can be used to affix the servomechanism 200 to another structure.

The housing top portion 202 can define a first interior chamber 218 and a second interior chamber 220. A first passage 222 can extend between the first interior chamber 218 chamber and the second interior chamber 220. A second passage 224 can extend between the first interior chamber and the second interior chamber. One or both the first passage 222 and the second passage 224 can be formed into the housing top portion 202 as pictured, but the present subject matter is not so limited, and other examples can include conduit, such as tubing, such as hose.

A vane 214 can be disposed in the first interior chamber 218. The present subject matter is not so limited, and other actuators can be disposed in the chamber, such as a piston to effect linear motion. For example, a piston can be disposed a chamber, with the first passage extending to one side, and the second passage extending to another side. Accordingly, the housing top portion 202 or another housing can function as a cylinder housing for a linear actuator.

As more clearly illustrated in FIGS. 2B-C, the vane can be coupled to an output shaft 204. The output shaft 204 can be rotably disposed in the housing top portion 202 with the at least one end of the output shaft exposed through the housing top portion 202. The output shaft 204 can be splined at one end 216.

Although the vane 214 is coupled to the output shaft 204, rotating around the same centerline as the output shaft 204 in use, the present subject matter is not so limited, and can include an output shaft that is coupled to the vane, to rotate with the vane, through a mechanism to translate motion such as a gear train.

The vane 214 can be coupled to the output shaft 204 and rotably disposed in the first chamber of the housing top portion 202 to sealingly reciprocally rotate inside the first chamber around a vane 214 axis. Clearance between an edge 246 of the vane 214 and the housing top portion 202 can be selected to control the amount of leakage between them. The clearance can be balanced with the capabilities of various manufacturing methods. In an example, cutting of the components, such as the housing top portion 202, can be done with rotating cutters positioned along one of two axes, which can cut down on complexity and therefore cost.

The vane 214 divides the first interior chamber 218 into a first variable volume portion 226 and a second variable volume portion 228. A first face 232 of the vane 214 can be parallel the vane axis 230, exposed to the first variable volume portion 226. The vane 214 can be rotably can be disposed in the first interior chamber 218 to reciprocate around a vane axis 230 with a sealing edge 246 of the vane parallel to the vane axis 230, and the output shaft 204 can be disposed to rotate around an output shaft axis. The vane axis and the output shaft axis are collinear as shown, but the present subject matter is not so limited. For example, the vane can be geared and mesh with gears on the output shaft.

A second face 234 of the vane 214, shown in FIG. 2D, can be parallel the vane axis, exposed to the second variable volume portion. The first passage 222 can open to the first variable volume portion 226. The second passage 224 opens to the second variable volume portion 228.

The first passage 222 and second passage 224 can form a fluid circuit with a pump such as a positive displacement pump, such as a reversible positive displacement pump. For example, the first passage 222 and second passage 224 can be in fluid communication with at least one rotor of a pump. The at least one rotor can be disposed in the second interior chamber 220 of the housing top portion 202 to sealingly rotate inside the second interior chamber 220. Such a pump can be comprised of a rotor housed in the housing top portion 202. A separate housing, other than the housing top portion 202, dedicated to housing one or more rotors can also be used. The first passage 222 can open to a first side of a rotor-housing seal and the second passage 224 can open to a second side of the rotor-housing seal. Thus, if the rotor is a screw-type rotor, the first passage 222 can open to one side, and the second passage 224 can open to another side.

The reversible positive displacement pump can be a gear pump 236 and the at least one rotor can be a first gear 238. A second gear 244 disposed in the second chamber to sealingly rotate inside the second chamber. The first passage 222 can open to a first side of a first-gear-to-second-gear seal 240 and the second passage 224 can open to a second side of the first-gear-to-second-gear seal 240. The first passage 222 can open to a first side of a second-gear-to-second-gear seal and the second passage 224 can open to a second side of the second-gear-to-second-gear seal.

An electric motor 208 is shown. The electric motor 208 can translate an electric signal into rotary motion. The electric motor 208 can be brushed, or brushless, and can be controlled using analog signals, digital signals, or a mix of the two types of signals. Motion of the motor can optionally be sensed, such as by a hall-effect sensor disposed internal to the motor. The electric motor 208 can be coupled to at least one rotor of the pump to turn the at least one rotor in two directions, with the first direction to increase pressure in the first variable volume portion, and the second direction to increase pressure in the second variable volume portion. Accordingly, the electric motor 208 can turn the first gear 238

An output shaft monitoring feedback transducer 210 can be coupled inside the housing top portion 202. The transducer 210 can be aligned to monitor an orientation of the output shaft 204 with respect to the housing top portion 202. A potentiometer can be used to transduce shaft motion to an electrical signal. The transducer 210 can monitor motion of a vane and translate that motion into an electric signal. The transducer 210 can provide analog signals, digital signals, or a mix of the two types of signals. The transducer 210 can include a mechanical adjustment that can be coupled to a vane. For example, when the component moves, it can mechanically adjust the transducer 210. Alternatively, the transducer signal can be provided via monitoring another portion of a system to which the servomechanism is connected. For example, if the servomechanism is coupled with a steering system, a sensor can monitor the position of the steering system and provide a transducer signal.

In some instances, this can include adjusting a conductive arm to contact one of or some of a plurality of contact patches, each of which carries a resistance that can be monitored by other electronics. Hence, if the transducer 210 is adjusted such that a rotable arm contacts point A, a first resistance is reported, and if it is adjusted such that a rotable arm contacts point B, another resistance can be report. Motion of the vane can motor can optionally be wirelessly sensed, such as by using hall-effect sensor or an optical sensor to monitor motion of the vane. The transducer 210 can be coupled to the electric motor 208 via electronics (not pictured) to input adjustments into the electric motor 208 to maintain the rotor of the electric motor 208 at a desired position.

FIG. 3 is a fluid circuit diagram showing an over-torque bleeding circuit of a servosaver, according to an example. A housing, such as housing top portion 202, can define a third passage 304. The third passage 304 can extend between a first passage 306 and a second passage 308. A first check valve 302 can be disposed in the third passage between the first passage 306 and the second passage 308. The first check valve 302 can be spring loaded via a coil spring 310, but the present subject matter is not so limited.

FIG. 4 is a fluid circuit diagram showing an over-torque bleeding circuit of a servosaver, according to an example. A housing, such as housing top portion 202, can define a fourth passage 404. The fourth passage 404 can extend between a first passage 406 and a second passage 408. A second check valve 402 can be disposed in the fourth passage between the first passage 406 and the second passage 408. The second check valve 402 can be spring loaded via a coil spring 410, but the present subject matter is not so limited.

The check valves of FIGS. 3 and 4 can be used separately or in combination. Each of the check valves can control the pressure in a respective passage. For example, if the shaft of a vane is over-torqued, pressure in a passage will rise, as a positive displacement pump will not provide for leakage as an open circuit pump would. Either the shaft or another component can fail, or the vane can move. Providing for a check valve from the over-pressured passage to the other passage can allow for the vane to move and relieve torque. In this way, the servomechanism acts like a servo-saver. Embodiments in which the pump is not positive displacement, and now over-pressure valving between the first passage and the second passage are also possible.

Returning to FIG. 2A, a fifth passage 250 can extend between the first passage 222 and the second passage 224, and to a reservoir 260. A housing, such as a second housing portion 248 shown in hidden line, can define the fifth passage 250. Fluid levels can be maintained via one-way valves configured to flow into the first passage and the second passage. An example of a reservoir system is shown schematically in FIG. 5.

FIG. 5 is a fluid circuit diagram showing a make-up reservoir, according to an example. A fifth passage 502 extends to each of a third check valve 510 and a fourth check valve 512. The third check valve 510 can be oriented to permit flow from the fifth passage 502 into the first passage 504. The fourth check valve can be oriented to permit flow from the fifth passage 502 to the second passage 506. The fifth passage can be in fluid communication with a reservoir 514.

The reservoir 514 can include a piston 516, which can be spring-loaded by a spring 520. The piston 516 can be sealed, such as with an o-ring 518, to a piston cavity 522 of a housing. The spring 520 can be disposed on an opposite side of a fluid-facing side 524 of the piston 516.

FIG. 6 is a cross section side view of a servomechanism, according to an example. A first output shaft seal 602 can be disposed between a top portion 604 of the output shaft 612 and the housing 606. A second output shaft seal 608 can be disposed between a bottom portion 610 of the output shaft 612 and the housing 606. The top end 614 of the output shaft 612 and the bottom end 616 of the output shaft 612 can be exposed to an exterior of the housing 606.

A first output shaft relief 618 can be disposed between the first output shaft seal 602 and the second output shaft seal 608 and between a top portion 604 of the output shaft 612 and the housing 606. A second output shaft relief 620 can be disposed between the first output shaft relief 618 and the second output shaft seal 608 and between a bottom portion 610 of the output shaft 612 and the housing 606.

These reliefs can be used to lessen the pressure on one or both of the first output shaft seal 602 and the second output shaft seal 608 by exposing the seals to tank or reservoir pressure. This can reduce leakage through the seals, which otherwise might occur if they were exposed to high pressure such as the pressure in one of the first and second passages opening to the vane chamber.

The sixth passage 622 can extend to the top portion 604 of the output shaft 612 and the bottom portion 610 of the output shaft 612. Each of the first output shaft relief 618 and the second output shaft relief 620 can be in fluid communication with a reservoir, such as via a sixth passage 622.

The relief can encircle the output shaft 612, at least partially. Alternatively the sixth passage 622 can have a width that can extend from one side of the output shaft to another side of the output shaft.

An electric motor 636 can be coupled to the at least one rotor disposed in the chamber 624 via a motor shaft 626. A motor shaft seal 628 can be disposed between the motor shaft 626 and the housing 606. The sixth passage 622 can extend to the motor shaft 626 landing between the at least one rotor and the motor shaft seal 628. The relief can encircle the motor shaft, at least partially. As pictured, the sixth passage 622 can have a width that can extend from one side of the motor shaft to another side of the motor shaft.

Motor control electronics 630 can be coupled to the housing in a dry portion 632 of the housing 606 interior outside of a fluid-retaining portion 634 of the housing 606. The electric motor 636 and the output shaft monitoring feedback transducer 638 can be disposed in the dry portion 632. The at least one end of the output shaft can be splined to mate with a servo horn.

FIG. 7A is a cross-section side view of a vane, according to an example. FIG. 7B is a bottom view of the vane illustrated in FIG. 7A. This detailed view of a vane shows a coupling 702 and a splined 704 output shaft 706. A central lumen 708 can be used to affix to a fastener to secure a servo horn to the output shaft 706. It can also be used to secure a transducer to the shaft. Additionally, it can be used to inspect the transducer from outside the servo without opening the servo.

FIG. 8A-E show views of a top portion of a housing portion 800. First 802, second 804, third 806, fourth 808 and fifth 810 passages are shown. Pilot holes leading to the passages, which are created during manufacturing, and which can be lated plugged, are also shown. A fill port 812 is shown which can be used to add fluid to the servomechanism during manufacture or repair. A channel 814 is shown, in which a seal such as an o-ring can be disposed to seal the housing portion 800 to another housing portion.

FIGS. 9A-D show views of a middle portion of a servomechanism housing portion 900, according to an example. A dry area 902 is shown. A reservoir 904 is shown, including passages 906 that can be used to connect the reservoir 904 to the first 802 and second 804 passages illustrated in FIG. 8C, among others.

Reliefs 908 can be disposed in the servomechanism housing portion 900 on at least one side of the first-gear-to-second-gear seal. These reliefs can reduce instances of the gear pump stalling, which can occur when high bulk modulus fluid becomes trapped between two gears. These reliefs provide escape paths for the fluid on sides of a sealed zone which seals against the pump and provides for compression of the fluid.

FIG. 10 is a bottom view of a middle portion 1000 of a servomechanism with components disposed therein, according to an example. A motor 1002 and a transducer 1004 are pictured. The reservoir 1006 is also pictured.

FIG. 11A is a top view of a bottom housing portion 1100, according to an example. FIG. 11B is side view of the housing portion of FIG. 11A. This bottom cover can include cavities 1102 that can be used to retain electronics and/or lighten the weight of the servomechanism.

FIG. 12A is a front view of a reservoir cover, according to an example. FIG. 12B is a cross-section right side view of the reservoir cover of FIG. 12A. The cover can have an opening 1202 that can be used to access the piston without removing the cover.

FIG. 13 is a cross-section side view of a reservoir piston, according to an example. The piston can include an o-ring groove 1302 and a threaded hole 1304 to receive a tool, such as a small threaded rod and nut used to keep the piston spring compressed during assembly of the system.

FIG. 14 is a flow chart showing a method of using a servomechanism, according to an example. At 1402, the method can include controlling a reversible positive displacement pump that can be located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that can be rotably disposed in a second chamber of a housing to rotate an output shaft that can be coupled to the vane. At 1404, the method can include controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to revers rotation of the output shaft.

A number of optional method steps are possible. At 1406, the method can optionally include making up fluid in the first and second passages with fluid from a reservoir in the housing that can be coupled via a third passage to each of the first passage and the second passage via one-way valves configured to flow into the first passage and the second passage. The method can include controlling the reversible positive displacement pump includes controlling a gear pump. The method can include controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing. The method can include controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing that can be coupled directly to the output shaft. The method can include controlling the reversible positive displacement pump includes controlling an electric motor, disposed in the housing, to rotate the reversible positive displacement pump.

FIG. 15 is a flow chart showing a method of assembling a servomechanism, according to an example. At 1502, the method can include forming a housing. An optional method can include defining a first interior chamber and a second interior chamber, with a first passage can extend between the first interior chamber and the second interior chamber and a second passage can extend between the first interior chamber and the second interior chamber.

At 1504, the method can include rotably disposing an output shaft in the housing with at least one end of the output shaft exposed through the housing.

At 1506, the method can include coupling a vane to the output shaft rotably disposed in the first chamber of the housing for sealingly reciprocally rotating inside the first chamber around a vane axis. In an optional method, the vane divides the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion. In an optional method, the first passage can open to the first variable volume portion and the second passage can open to the second variable volume portion.

At 1508, the method can include disposing at least one rotor of a reversible positive displacement pump in the second chamber of the housing, the at least one rotor for sealingly rotating inside the second chamber. In an optional method, the first passage can open to a first side of a rotor-housing seal and the second passage can open to a second side of the rotor-housing seal.

At 1510, the method can include disposing an electric motor inside the housing, the electric motor for rotating the at least one rotor.

At 1512, the method can include disposing an output shaft monitoring feedback transducer inside the housing in alignment with the housing and the output shaft, the output shaft monitoring feedback transducer for monitoring an orientation of the output shaft with respect to the housing. An optional method can include disposing at least one rotor of a reversible positive displacement pump includes disposing a gear pump in the housing. In an optional method, a first-gear-to-second-gear seal of the gear pump can define a gear pump interface chamber, and forming the housing includes forming a relief proximal the gear pump interface chamber to provide a leakage path out of the gear pump interface chamber into a remainder of a fluid-retaining portion of the housing.

ADDITIONAL NOTES & EXAMPLES

Example 1 includes subject matter (such as an apparatus, a method, a means for performing acts, or a device readable medium including instructions that, when performed by the device, can cause the device to perform acts), including a method of using a servomechanism, including controlling a reversible positive displacement pump that is located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that is rotably disposed in a second chamber of a housing to rotate an output shaft that is coupled to the vane. The example can include, or can optionally be combined with the subject matter of Example 1 to optionally include controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to reverse rotation of the output shaft.

Example 2 can include, or can optionally be combined with the subject matter of one or any combination of Examples 1 through 2 to optionally include making up fluid in the first and second passages with fluid from a reservoir in the housing that is coupled via a third passage to each of the first passage and the second passage via one-way valves configured to flow into the first passage and the second passage.

Example 3 can include, or can optionally be combined with the subject matter of one or any combination of Examples 1 through 2 wherein controlling the reversible positive displacement pump includes controlling a gear pump.

Example 4 can include, or can optionally be combined with the subject matter of one or any combination of Examples 1 through 3 wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing.

Example 5 can include, or can optionally be combined with the subject matter of one or any combination of Examples 1 through 4 wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing that is coupled directly to the output shaft.

Example 6 can include, or can optionally be combined with the subject matter of one or any combination of Examples 1 through 5 wherein controlling the reversible positive displacement pump includes controlling an electric motor, disposed in the housing, to rotate the reversible positive displacement pump.

Example 7 includes subject matter (such as an apparatus, a method, a means for performing acts, or a device readable medium including instructions that, when performed by the device, can cause the device to perform acts), including a method of assembling a servomechanism, including forming a housing by defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber.

Example 8 can include, or can optionally be combined with the subject matter of one or any combination of Example 7 to optionally include rotably disposing an output shaft in the housing with at least one end of the output shaft exposed through the housing.

Example 9 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 8 to optionally include coupling a vane to the output shaft rotably disposed in the first chamber of the housing for sealingly reciprocally rotating inside the first chamber around a vane axis.

Example 10 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 9 wherein the vane divides the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion.

Example 11 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 10 wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion.

Example 12 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 11 to optionally include disposing at least one rotor of a reversible positive displacement pump in the second chamber of the housing, the at least one rotor for sealingly rotating inside the second chamber.

Example 13 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 12 wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal.

Example 14 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 13 to optionally include disposing an electric motor inside the housing, the electric motor for rotating the at least one rotor.

Example 15 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 14 to optionally include disposing an output shaft monitoring feedback transducer inside the housing in alignment with the housing and the output shaft, the output shaft monitoring feedback transducer for monitoring an orientation of the output shaft with respect to the housing.

Example 16 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 15 wherein disposing at least one rotor of a reversible positive displacement pump includes disposing a gear pump in the housing.

Example 17 can include, or can optionally be combined with the subject matter of one or any combination of Examples 7 through 16 wherein a first-gear-to-second-gear seal of the gear pump defines a gear pump interface chamber, and forming the housing includes forming a relief proximal the gear pump interface chamber to provide a leakage path out of the gear pump interface chamber into a remainder of a fluid-retaining portion of the housing.

Example 18 includes subject matter (such as an apparatus, a method, a means for performing acts, or a device readable medium including instructions that, when performed by the device, can cause the device to perform acts), including a housing defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber.

Example 19 can include, or can optionally be combined with the subject matter of one or any combination of Example 18 to optionally include an output shaft rotably disposed in the housing with at least one end of the output shaft exposed through the housing.

Example 20 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 19 to optionally include vane coupled to the output shaft and rotably disposed in the first chamber of the housing to sealingly reciprocally rotate inside the first chamber around a vane axis.

Example 21 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 20 wherein the vane divides the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion.

Example 22 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 21 wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion.

Example 23 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 22 to optionally include at least one rotor of a reversible positive displacement pump disposed in the second chamber of the housing to sealingly rotate inside the second chamber.

Example 24 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 23 wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal.

Example 25 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 24 to optionally include an electric motor coupled inside the housing to the at least one rotor to turn the at least one rotor.

Example 26 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 25 to optionally include output shaft monitoring feedback transducer coupled inside the housing and aligned to monitor an orientation of the output shaft with respect to the housing.

Example 27 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 26 wherein the electric motor is a brushless electric motor.

Example 28 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 27 wherein the reversible positive displacement pump is a gear pump and the at least one rotor is a first gear.

Example 29 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 28 to optionally include a second gear disposed in the second chamber to sealingly rotate inside the second chamber.

Example 30 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 29 wherein the first passage opens to a first side of a first-gear-to-second-gear seal and the second passage opens to a second side of the first-gear-to-second-gear seal.

Example 31 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 30 wherein reliefs are disposed in the housing on at least one side of the first-gear-to-second-gear seal.

Example 32 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 31 wherein the output shaft monitoring feedback transducer includes a hall effect sensor to monitor a portion of the output shaft.

Example 33 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 32 wherein the output shaft monitoring feedback transducer includes a potentiometer coupled to the output shaft.

Example 34 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 33 wherein the electric motor is coupled to the at least one rotor to turn the at least one rotor in two directions, with the first direction to increase pressure in the first variable volume portion, and the second direction to increase pressure in the second variable volume portion.

Example 35 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 34 wherein an exterior profile of the servomechanism is sized to be disposed in a space sized to receive a geared hobby servomechanism.

Example 36 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 35 wherein the housing defines a third passage extending between the first passage and the second passage, with a first check valve disposed in the third passage between the first passage and the second passage.

Example 37 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 36 wherein the housing defines a fourth passage extending between the first passage and the second passage, with a second check valve disposed in the fourth passage between the first passage and the second passage,

Example 38 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 37 wherein the first check valve is oriented to permit flow from the first passage to the second passage, and the second check valve is oriented to permit flow from the second passage to the first passage, the first check valve and second check valve.

Example 39 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 38 wherein the servomechanism functions as a servosaver.

Example 40 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 39 wherein a fifth passage extends to each of a third check valve and a fourth check valve, with the third check valve oriented to permit flow from the fifth passage into the first passage, and the fourth check valve oriented to permit flow from the fifth passage to the second passage, the fifth passage in fluid communication with a reservoir.

Example 41 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 40 wherein the reservoir comprises a spring-loaded piston sealed to a piston cavity of the housing, with the spring disposed on an opposite side of a fluid-facing side of the piston.

Example 42 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 41 to optionally include a first output shaft seal disposed between a top portion of the output shaft and the housing and a second output shaft seal disposed between a bottom portion of the output shaft and the housing.

Example 43 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 42 wherein the top end of the output shaft and the bottom end of the output shaft are exposed to an exterior of the housing.

Example 44 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 43 to optionally include a first output shaft relief disposed between the first output shaft seal and the second output shaft seal and between a top portion of the output shaft and the housing and a second output shaft relief disposed between the first output shaft relief and the second output shaft seal and between a bottom portion of the output shaft and the housing, with each of the first output shaft relief and the second output shaft relief in fluid communication with a reservoir via a sixth passage.

Example 45 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 44 wherein the electric motor is coupled to the at least one rotor via a motor shaft.

Example 46 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 45 to optionally include a motor shaft seal disposed between the motor shaft and the housing.

Example 47 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 46 wherein the sixth passage extends to the motor shaft between the at least one rotor and the motor shaft seal.

Example 48 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 47 to optionally include a sixth passage extending to the top portion of the output shaft and the bottom portion of the output shaft, the six passage having a width extending from one side of the output shaft to another side of the output shaft.

Example 49 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 48 to optionally include motor control electronics coupled to the housing in a dry portion of the housing interior outside of a fluid-retaining portion of the housing extending between the first seal and the second output shaft seal.

Example 50 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 49 wherein the electric motor and the output shaft monitoring feedback transducer are disposed in the dry portion.

Example 51 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 50 wherein the vane is rotably disposed in the first chamber to reciprocate around a vane axis with a sealing edge of the vane parallel to the vane axis, and the output shaft is disposed to rotate around an output shaft axis.

Example 52 can include, or can optionally be combined with the subject matter of one or any combination of Examples 18 through 51 wherein the vane axis and the output shaft axis are collinear.

Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples.

The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in that may be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “An and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is to allow the reader to quickly ascertain the nature of the technical disclosure, for example, to comply with 37 C.F.R. §1.72(b) in the United States of America. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the embodiments should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

What is claimed is:
 1. A method of using a servomechanism, comprising: controlling a reversible positive displacement pump that is located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that is rotably disposed in a second chamber of a housing to rotate an output shaft that is coupled to the vane; and controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to revers rotation of the output shaft.
 2. The method of claim 1, comprising making up fluid in the first and second passages with fluid from a reservoir in the housing that is coupled via a third passage to each of the first passage and the second passage via one-way valves configured to flow into the first passage and the second passage.
 3. The method of claim 1, wherein controlling the reversible positive displacement pump includes controlling a gear pump.
 4. The method of claim 3, wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing.
 5. The method of claim 4, wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing that is coupled directly to the output shaft.
 6. The method of claim 1, wherein controlling the reversible positive displacement pump includes controlling an electric motor, disposed in the housing, to rotate the reversible positive displacement pump.
 7. A method of assembling a servomechanism, comprising: forming a housing by defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber; rotably disposing an output shaft in the housing with at least one end of the output shaft exposed through the housing; coupling a vane to the output shaft rotably disposed in the first chamber of the housing for sealingly reciprocally rotating inside the first chamber around a vane axis, the vane dividing wherein the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion, wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion; disposing at least one rotor of a reversible positive displacement pump in the second chamber of the housing, the at least one rotor for sealingly rotating inside the second chamber, wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal; disposing an electric motor inside the housing, the electric motor for rotating the at least one rotor; and disposing an output shaft monitoring feedback transducer inside the housing in alignment with the housing and the output shaft, the output shaft monitoring feedback transducer for monitoring an orientation of the output shaft with respect to the housing.
 8. The method of claim 7, wherein disposing at least one rotor of a reversible positive displacement pump includes disposing a gear pump in the housing.
 9. The method of claim 8, wherein a first-gear-to-second-gear seal of the gear pump defines a gear pump interface chamber, and forming the housing includes forming a relief proximal the gear pump interface chamber to provide a leakage path out of the gear pump interface chamber into a remainder of a fluid-retaining portion of the housing.
 10. A servomechanism, comprising: a housing defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber; an output shaft rotably disposed in the housing with at least one end of the output shaft exposed through the housing; a vane coupled to the output shaft and rotably disposed in the first chamber of the housing to sealingly reciprocally rotate inside the first chamber around a vane axis, wherein the vane divides the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion, wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion; and at least one rotor of a reversible positive displacement pump disposed in the second chamber of the housing to sealingly rotate inside the second chamber, wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal; an electric motor coupled inside the housing to the at least one rotor to turn the at least one rotor; and an output shaft monitoring feedback transducer coupled inside the housing and aligned to monitor an orientation of the output shaft with respect to the housing.
 11. The servomechanism of claim 10, wherein the reversible positive displacement pump is a gear pump and the at least one rotor is a first gear, and comprising a second gear disposed in the second chamber to sealingly rotate inside the second chamber, wherein the first passage opens to a first side of a first-gear-to-second-gear seal and the second passage opens to a second side of the first-gear-to-second-gear seal.
 12. The servomechanism of claim 10, wherein an exterior profile of the servomechanism is sized to be disposed in a space sized to receive a geared hobby servomechanism and wherein the at least one end of the output shaft is splined to mate with a servo horn.
 13. The servomechanism of claim 10, wherein the housing defines a third passage extending between the first passage and the second passage, with a first check valve disposed in the third passage between the first passage and the second passage.
 14. The servomechanism of claim 13, wherein the housing defines a fourth passage extending between the first passage and the second passage, with a second check valve disposed in the fourth passage between the first passage and the second passage, wherein the first check valve is oriented to permit flow from the first passage to the second passage, and the second check valve is oriented to permit flow from the second passage to the first passage, the first check valve and second check valve comprising a servosaver.
 15. The servomechanism of claim 10, wherein a fifth passage extends to each of a third check valve and a fourth check valve, with the third check valve oriented to permit flow from the fifth passage into the first passage, and the fourth check valve oriented to permit flow from the fifth passage to the second passage, the fifth passage in fluid communication with a reservoir.
 16. The servomechanism of claim 15, wherein the reservoir comprises a spring-loaded piston sealed to a piston cavity of the housing, with the spring disposed on an opposite side of a fluid-facing side of the piston.
 17. The servomechanism of claim 15, comprising a first output shaft seal disposed between a top portion of the output shaft and the housing and a second output shaft seal disposed between a bottom portion of the output shaft and the housing, wherein a top end of the output shaft and a bottom end of the output shaft are exposed to an exterior of the housing.
 18. The servomechanism of claim 17, comprising a first output shaft relief disposed between the first output shaft seal and the second output shaft seal and between a top portion of the output shaft and the housing and a second output shaft relief disposed between the first output shaft relief and the second output shaft seal and between a bottom portion of the output shaft and the housing, with each of the first output shaft relief and the second output shaft relief in fluid communication with a reservoir via a sixth passage.
 19. The servomechanism of claim 18, wherein the electric motor is coupled to the at least one rotor via a motor shaft, and comprising a motor shaft seal disposed between the motor shaft and the housing.
 20. The servomechanism of claim 19, wherein the sixth passage extends to the motor shaft between the at least one rotor and the motor shaft seal. 